Anniversaries

I wonder what aliens would think of the human penchant for celebrating anniversaries.

"As far as we can tell, you take some event, then you wait for this huge rock you call the earth to circle the entire sun once, and then you make a fuss about the event again by spending lots of money on stuff your people make? Every time this rock circles the sun? Year after year after year after year?"

That's it.

"Please forgive us. We had no idea you were such an advanced civilization."